The invention relates to a wire press-fitting method and apparatus for a pressure terminal adapted to connect a sheathed wire into pressuring blades of the pressure terminal by pressure.
Generally, a pressure terminal is connected as follows. A sheathed wire is pressed into the slots of platelike pressuring blades by a pressuring punch; edges of the pressuring blades cut the sheath of the wire by the pressing force, so that the conductors are exposed; and then both the edges of the pressuring blades and the conductors of the wire are pressured to establish connection providing electric conduction.
Such a wire press-fitting process consists of two steps. The first step is to insert a pressure terminal into a connector housing (hereinafter referred to as "housing"), and the second step is to connect a wire to the pressure terminal inserted into the housing by pressure.
An example of the first step, which is the step of inserting the pressure terminal into the housing, is disclosed in Unexamined Japanese Patent Publication No. Hei. 4-33285. Longitudinally catenated pressure terminals wound in a reel are inserted sequentially from the head end thereof into terminal accommodating chambers continuously from the rear toward the front of the housing, and the catenating strips are thereafter cut off.
Further, an example of the second step, which is the step of pressuring the wire into the pressure terminal within the terminal accommodating chamber, is disclosed in Unexamined Japanese Utility Model Publication Nos. Hei. 4-48568 and Sho. 61-136484. The pressure terminal inserted in the insertion process is fixed at a predetermined position, and the wire is thereafter connected to the pressure terminal by pressure.
FIGS. 9 and 10 are a perspective view and a sectional view outlining such wire press-fitting process. The whole process will be described with reference to these figures. First, a pressure terminal 105 is inserted into a housing 106 from the rear of the housing 106. The pressure terminal 105 is to be inserted as far as to the front of the housing 106. Since the pressure terminal 105 has a downwardly projecting lance 108 at the tip thereof, an appropriate clearance a is provided in an upper part of the terminal accommodating chamber 107 to receive the lance 108. The pressure terminal 105 is fixed at a correct position by a positioning tool after being inserted, and a wire 103 is then pressed into the pressure terminal 105 by a pressuring punch 104 from above, the pressuring punch being fitted into a vertically movable press main body 113.
The pressuring punch 104 pushes the wire 103 down together with the sheath of the wire 103 so that the wire 103 is pressed into slots of pressuring blades 102. At this instance, the sheath of the wire 103 is cut apart by the edges of the slots so that the conductors of the wire 103 are electrically connected to the pressuring blades 102. Since the pressuring punch 104 has releasing grooves 110 formed therein, the pressuring blades 102 are fitted into these releasing grooves 110 so that interference between the pressuring punch 104 and the pressuring blades can be avoided.
However, such conventional wire press-fitting method has encountered the problem that the pressure terminal sometimes plays inside the housing after the insertion thereof because of the clearance a provided to insert the pressure terminal into the front of the housing from the rear of the housing as shown in, e.g., FIG. 10.
As a result, in the case of performing the operation of setting the pressure terminal 105 at a predetermined position by causing the projected end of the positioning tool 111 to be abutted against the front opening of the housing 106 so that the pressure terminal 105 can be pushed back as shown in FIG. 11, the rear part of the pressure terminal 105 may, in some cases, float as shown in FIG. 11, and from this may arise incomplete connection and difficulties in connection during the wire press-fitting process.
Further, in the wire press-fitting process, if the sheath of the wire 103 is, e.g., thick or the sheathing material is relatively rigid, or the pressuring blades 102 do not function as a good cutter, then the side walls of the pressuring blades 102 may be expanded toward cavity walls 122 as shown in FIG. 12. In addition, if the pressuring blades 102 are plastically deformed so as to lose restitutive force by going beyond the elastic deformable range thereof, contact between the wire and the pressuring blades is not so adequate, which in turn makes it difficult to ensure electric contact between the conductors of the wire 103 and the pressuring blades 102.
Still further, since the expanded pressuring blades 102 cause the cavity walls 122 of the housing to be inclined, the adjacent cavity walls are affected by such inclined cavity walls. This may, in certain cases, make it impossible to connect the wire to the pressure terminal by pressure.
Hence, for the aforementioned reasons, there exist the problems such as a reduction in nondefectives in the mass production process, a limited freedom in designing due to limited kinds of material that can be used, and an elevated cost of manufacture.